Although there is a long-demonstrated association between obesity and depression, a new gene study reveals that some overweight people may, in fact, be programmed to not have depression.

According to the study by McMaster University, the gene FTO — known to be a strong contributor to obesity — is also linked to an 8 percent reduction in a person’s risk for depression.

“The difference of eight percent is modest and it won’t make a big difference in the day-to-day care of patients,” said senior author David Meyre, associate professor in clinical epidemiology and biostatistics at the Michael G. DeGroote School. “But, we have discovered a novel molecular basis for depression.”

The researchers looked at data from the larger EpiDREAM study led by the Population Health Research Institute. They analyzed the genetic and psychiatric status of more than 17,000 individuals, with DNA samples coming from 21 different countries.

The findings revealed that patients previously found to have the genetic variant FTO also had an 8 percent lower risk for depression.

The results were somewhat unexpected.

“We set out to follow a different path, starting from the hypothesis that both depression and obesity deal with brain activity,” said Meyre. “We hypothesized that obesity genes may be linked to depression.”

Previous research has suggested that not only are obese people more likely to be depressed, but depressed people are more likely to become obese.

The research, conducted by Sarah M. Markowitz, M.S., found that individuals who suffer from depression are more likely to become obese because of physiological changes in hormones and the immune system.

Also, those who are already obese are likely to become depressed because of poor health, self-esteem and dissatisfaction with appearance.

“The treatment of depression and obesity should be integrated,” the authors concluded in a statement. “This way, healthcare providers are working together to treat both conditions, rather than each in isolation.”

But while evidence suggests that being obese may lead to depression, genetically, FTO is still associated with a lower risk for the disorder, which may explain why some overweight individuals are optimistic despite poor health and poor self-esteem.